First of all, a frame structure according to a related art is described with reference to FIG. 1 as follows. FIG. 1 is a diagram of a frame structure of IEEE (institute of electrical and electronics engineers) 802.16m system.
Referring to FIG. 1, a single superframe consists of 4 frames. And, each of the frames consists of 8 subframes. Moreover, each of the subframes consists of 5 or 6 OFDM (orthogonal frequency division multiplexing) symbols in accordance with a length of a cyclic prefix (hereinafter abbreviated CP).
A first subframe of the superframe includes a superframe header (hereinafter abbreviated SFH). And, the SFH includes essential system parameters and system configuration information. The SFH can be divided into a primary superframe header (hereinafter abbreviated P-SFH) and a secondary superframe header (hereinafter abbreviated S-SFH). The P-SFH is transmitted each superframe. And, information contained (or included) in the S-SFH is divided into a plurality of subpackets. And, a plurality of the subpackets differ from each other in transmission period.
Additional system information except the system information carried on the SFH is transmitted on a traffic channel. And, additional broadcast information carried on the traffic channel includes an extended system parameter & system configuration information and a signaling for downlink announcement.
The extended system parameter & system configuration information includes a system configuration parameter & information, which is not essential for a mobile station to access a network, used by the mobile station after completion of the access to the network. For instance, the extended system parameter & system configuration information includes information for handover, information for MIMO (multiple input multiple output) antenna, information for a relay, information for a femto cell, information for EMBS, information for inter-RAT, information on neighbor cells and the like. The signaling for the downlink announcement is to provide a network indication to a mobile station in idle or sleep mode.
Broadcast messages including the additional system information in IEEE 802.16m system include SCD (system configuration descriptor) message, NBR-ADV (neighbor advertisement) message, TRF-IND (traffic indication) message, PAG-ADV (BS broadcast paging) message, PGID (paging ID) information message, SS network CLK-CMP (clock comparison) message, SII-ADV (service identity broadcast) message, and LBS-ADV (location information broadcast for LBS) message.
The SCD message includes the information for the handover, the information for the MIMO, the information for the EMBS, and the information for the inter-RAT.
However, according to the related art, since a mobile station is not aware of a transmission timing point of a broadcast message including additional system information, it should decode the broadcast message each time to obtain a latest addition system information. Besides, if mobile stations in idle or sleep mode keep monitoring a presence or non-presence of a message until receiving a broadcast message including additional system information, it is inefficient in aspect of power saving. Meanwhile, a transmission delay occurs until the mobile station having entered an active mode from the idle or sleep mode receives the broadcast message including the additional system information. Besides, the mobile station needs to be aware whether to apply the additional system information contained in the broadcast message and also needs to be aware of a timing point of the application of the additional system information.